(1) Field of the Invention
The present invention relates to an organic electroluminescent display with high resolution.
(2) Description of the Related Art
Each pixel of the typical organic electroluminescent display includes two transistors and one capacitor. The area ratio of the transistors and the capacitor covering the whole pixel can affect the size of the light-emitting region. For example, comparing two displays with the same size, the one with higher resolution has smaller pixel size than the other one. As the pixel size is reduced, the transistors and the capacitor cover more area of the pixel. Whereupon the area used to emit light is getting small in the pixel. When the pixel size is getting small until no perfect region provided for light passing, the light only accesses the gaps between the transistors and the wires.
FIG. 1A is a conventional organic electroluminescent display. Each pixel 110 of the organic electroluminescent display 100 has a switching transistor 111, a driving transistor 112, a capacitor 113 and an organic light emitting diode 114. As the size of the pixel 110 is large enough, the organic light emitting diode 114, transistors 111 and 112, and the capacitor 113 do not overlap with each other, so it has a perfect light-emitting region.
FIG. 1B is another organic electroluminescent display 200 with higher resolution than the organic electroluminescent display 100 shown in FIG. 1A. Each pixel 210 of the organic electroluminescent display 200 includes a switching transistor 211, a driving transistor 212, a capacitor 213 and an organic light emitting diode 214. Unlike FIG. 1A, the organic light emitting diode 214 overlaps with the transistors 211, 212, or the capacitor 213. The physical light-emitting region is only a gap between the transistors 211, 212 and the capacitor 213.
FIG. 1C is a sectional view of the display 200 shown in FIG. 1B. Its fabricating process comprises forming the components such as transistors 211, 212 etc. on the substrate (not numbered); next forming an ITO layer 214a on the forgoing components; and forming a cap layer 215 by a photo mask to define a opening region 216. As shown, the wires, the transistors or the capacitors cover a part of the opening region 210, so the light cannot exit through the part, and the top view of the opening region 216 can refer to FIG. 1D.
To sum up, when the pixel size is getting small until no perfect region provided for light passing, the light only accesses the gap between the transistors and the wires. If the opening region of the cap layer includes some non-light-emitting regions, it may still consume the power, but generate no brightness.